Activated carbon derived from carbon residue from biomass gasification and its application for dye adsorption: Kinetics, isotherms and thermodynamic studies

The plasma assisted preparation of Fe-MOFs with high adsorption capacity

The plasma preparation of MOF-235

Alginate-based composites for environmental applications: A critical review

Alginate-based composites have been extensively studied for applications in energy and environmental sectors due to their biocompatible, nontoxic, and cost-effective properties. This review is designed to provide an overview of the synthesis and application of alginate-based composites. In addition to an overview of current understanding of alginate biopolymer, gelation process, and cross-linking mechanisms, this work focuses on adsorption mechanisms and performance of different alginate-based composites for the removal of various pollutants including dyes, heavy metals, and antibiotics in water and wastewater. While encapsulation in alginate gel beads confers protective benefits to engineered nanoparticles, carbonaceous materials, cells and microbes, alginate-based composites typically exhibit enhanced adsorption performance. The physical and chemical properties of alginate-based composites determine the effectiveness under different application conditions. A series of alginate-based composites and their physicochemical and sorptive properties have been summarized. This critical review not only summarizes recent advances in alginate-based composites but also presents a perspective of future work for their environmental applications.

Steam activation of waste biomass: highly microporous carbon, optimization of bisphenol A, and diuron adsorption by response surface methodology

Highly microporous carbons were prepared from argan nut shell (ANS) using steam activation method. The carbons prepared (ANS@H2O-30, ANS@H2O-90, and ANS@H2O-120) were characterized using X-ray diffraction, scanning electron microscopy, Fourier-transform infrared, nitrogen adsorption, total X-ray fluorescence, and temperature-programmed desorption (TPD). The ANS@H2O-120 was found to have a high surface area of 2853 m2/g. The adsorption of bisphenol A and diuron on ANS@H2O-120 was investigated. The isotherm data were fitted using Langmuir and Freundlich models. Langmuir isotherm model presented the best fit to the experimental data suggesting micropore filling of ANS@H2O-120. The ANS@H2O-120 adsorbent demonstrated high monolayer adsorption capacity of 1408 and 1087 mg/g for bisphenol A and diuron, respectively. The efficiency of the adsorption was linked to the porous structure and to the availability of the surface adsorption sites on ANS@H2O-120. Response surface method was used to optimize the removal efficiency of bisphenol A and diuron on ANS@H2O-120 from aqueous solution. Graphical abstract ᅟ.

Adsorptive removal of adsorbable organic halogens by activated carbon

Current research mainly focuses on the reduction of adsorbable organic halogen (AOX) sources, while studies on AOX monitoring and management in the environment are scarce. Organic pollutants in water are mainly fixed by sediments. Thus, in this paper, activated carbon was used to simulate the adsorption of AOX by sediments. AOX volatilization and degradation were also studied to exclude their effect on adsorption. Micromolecule chlorides were more easily volatilized and degraded than chlorobenzene and chlorophenol. The adsorption of activated carbon to AOX in bleaching wastewater was also studied and the optimum conditions for AOX removal were elucidated (particle size, 62 µm; time, 120 min; pH, 2.5; temperature, 40°C; and activated carbon dosage, 1.75 g l-1). AOX adsorption by activated carbon is a chemical process. Hence, the chemical compositions of the bleaching effluent with and without adsorption were analysed by GC-MS. The results revealed that activated carbon exhibits a good AOX removal effect, thereby providing a theoretical basis for monitoring the AOX distribution in the environment.

A novel mesoporous zeolite-activated carbon composite as an effective adsorbent for removal of ammonia-nitrogen and methylene blue from aqueous solution

A mesoporous zeolite-activated carbon composite (Z-AC) was prepared by hydrothermal synthesis method for both ammonia-nitrogen (NH₃-N) and methylene blue (MB) removal from aqueous solution. For Z-AC with the reparation temperature of 90 °C and kaolin/AC = 4, the adsorption capacity of MB (754.75 mg/g, 298 K) was 83% of that for pure AC, and the adsorption capacity of NH₃-N were 9.00 mg/g, which was higher than that for AC and Z (the kaolin after hydrothermal treatment). The Z-AC exhibited obvious mesoporous structure, the S_BET of the Z-AC (378 cm²/g) was 31% of that for AC (1215 cm²/g). The introduction of a small amount of AC into Z increased the S_BET of Z, thus, the adsorption capacity of MB was improved dramatically. On the other hand, the dispersion of Z was enhanced by adding AC, which promoted the contact between Z and NH₃-N, and then led to improvement of the NH₃-N adsorption.

Mechanistic insight into protein supported biosorption complemented by kinetic and thermodynamics perspectives

In this review, we discussed the micro-level aspects of protein supported biosorption. The mechanism, surface chemistry in terms of energy interactions and electron transfer process (ETP) of peptide systems within protein are three important areas that provide mechanistic insight into protein supported biosorption. The functional groups in proteinous material like hydroxyl (-OH), carbonyl (>C=O), carboxyl (-COOH) and sulfhydryl (-SH) play a significant role in the biosorption of variety of pollutants such as metal ions, metalloids, and organic matters in wastewaters. The mechanistic aspects of biosorption are crucial not only for the separation process but also they contribute towards stoichiometric considerations and mathematical modelling process. The surface chemistry of applied biosorbents relies on interfacial components whose interaction energies are estimated with help of classical Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory mathematically. Proteins are the fundamental molecules of many biomaterial used for the biosorption of contaminents and peptide bond is considered as the backbone of proteins. The charge variations on peptide bonding is the result of ETP whose discussion was made part of this review for understaning number of biological and technological processes of vital interests. In addition, this review was complemented by exhaustive overview of kinetic and thermodynamics perspectives of biosorption process.

Paper pulp-based adsorbents for the removal of pharmaceuticals from wastewater: A novel approach towards diversification

In this work, two pulps, bleached (BP) and raw pulp (RP), derived from the paper production process, were used as precursors of non-activated and activated carbons (ACs). In the case of non-ACs, the production involved either pyrolysis or pyrolysis followed by acid washing. For ACs production, the pulps were impregnated with K₂CO₃ or H₃PO₄, and then pyrolysed and acid washed. After production, the materials were physically and chemically characterized. Then, batch adsorption tests on the removal of two pharmaceuticals (the anti-epileptic carbamazepine (CBZ) and the antibiotic sulfamethoxazole (SMX)) from ultra-pure water and from Waste Water Treatment Plant (WWTP) effluents were performed. In ultra-pure water, non-ACs were not able to adsorb CBZ or SMX while ACs showed good adsorption capacities. In WWTP effluents, although ACs satisfactorily adsorbed CBZ and SMX, they showed lower adsorption capacities for the latter. Tests with WWTP effluents revealed that the best adsorption capacities were achieved by carbons produced from BP and activated with H₃PO₄: 92±19mgg^-1 for CBZ and 13.0±0.6mgg^-1 for SMX. These results indicate the potential of paper pulps as precursors for ACs that can be applied in wastewater treatment.

Bioethanol Production From Hydrolyzed Lignocellulosic After Detoxification Via Adsorption With Activated Carbon and Dried Air Stripping

Bioethanol production has been presented as an alternative for supplying energy demand and minimizing greenhouse gases effects. However, due to abrasively conditions employed on the biomass during pretreatment and hydrolysis processes, inhibitors for fermentation phase such as acetic acid and others can be generated. Based on this problem, the aim of this work was to evaluate the adsorption of acetic acid on microporous activated carbon and investigate the stripping of the same component with dried air. For adsorption process, three concentrations of acetic acid (5, 10, and 20%) were analyzed by adsorption kinetics and adsorption isotherms (Langmuir and Freundlich models). Pseudo-second order model showed to fit better when compared to Pseudo-first order model. The Intraparticle Diffusion model presented the first phase of the adsorption as the regulating step of the adsorption process. The Langmuir model showed the best fitting, and the maximum capacity of adsorption was found as 128.66 mg.g^-1. For stripping procedure an apparatus was set in order to insert dried air by a diffusor within the solution in study. Increasing temperature showed to be determinant on augmenting acetic acid evaporation in 2.14 and 6.22 times for 40 and 60°C when comparing it to 20°C. The application of the pickling process for removal of fermentation inhibitors in sugarcane bagasse hydrolyzed allowed the production 8.3 g.L^-1 of ethanol.

Adsorption behavior of Ni(II) onto activated carbons from hide waste and high-pressure steaming hide waste

This work reports the preparation and adsorption of Ni(II) via activated carbons which produced from hide waste (HWAC) and high-pressure steaming hide waste (HWSAC) with potassium silicate as the activating agent. The best preparation condition for HWAC and HWSAC was the activation temperature of 700 °C using an impregnation ratio of 2:1. Both of them were characterized by N₂ adsorption/desorption isotherms, SEM and FT-IR spectra. The surface area of HWAC and HWSAC was 1804.37 and 1361.26 m²/g, respectively. Despite the surface area of HWAC being larger than that of HWSAC, but the adsorption capacity of Ni(II) for HWAC was lower than that for HWSAC. Furthermore, the adsorption capacity of Ni(II) for both HWAC and HWSAC showed pH-dependent behavior and increased with the increase in pH value, which can be attributed to the functional groups of HWAC and HWSAC materials through the electrostatic attraction. The adsorption data for HWAC and HWSAC were fitted with four isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and four kinetic models (pseudo-first order model, pseudo-second order model, intra-particle diffusion and Elovich equation), indicating that Langmuir isotherm and Pseudo-second order model fitted well with high coefficient of determination (R² > 0.99) for both the two adsorbents. The positive enthalpy of adsorption (ΔH) and free energy of adsorption (ΔG) indicate a spontaneous and endothermic nature of the process. These results demonstrated that activated carbon can be prepared from hide waste which could remove heavy metal such as Ni(II) effectively.

Superior amine-rich gel adsorbent from peach gum polysaccharide for highly efficient removal of anionic dyes

Herein, we demonstrated the potential of peach gum polysaccharide-based amine-rich gel (ARG) as an efficient adsorbent for removal of anionic dyes from water. The adsorption performance of ARG was systematically studied by choosing methyl orange (MO) and amaranth (ART) as representative anionic dyes. The effects of various parameters such as pH, ionic strength, temperature, initial dye concentration and contact time on the adsorption were investigated. The ARG exhibited superior adsorption selectivity and stable adsorption behaviors against variation of pH and ionic strength for anionic dyes. Adsorption process reached equilibrium within 10 min and showed good correlation with pseudo-second-order kinetic model and Langmuir isotherm. The adsorption capacity of ARG for MO and ART can reach 1949.5 and 1082.2 mg g^-1, respectively. Based on its sustainable characteristic, low cost and excellent adsorption property, the ARG holds great promise for utilizing as an adsorbent for practical water treatment applications.

Synthesis and characterization of the removal of organic pollutants in effluents

The use of a large number of organic pollutants results in the accumulation of effluents at the places of production and the environment. These substances are, therefore, dangerous for living organisms and can cause heavy environmental damage. Hence, to cure these problems certain methods were used for the elimination of organic effluents. Indeed, the methods of elimination through magnetic adsorption and/or separation prove to be effective in the treatment of certain wastes, but the effectiveness of each one of these methods depends on several characteristics and also present limitations according to the pollutants they adsorb. This review examines on the one hand the capacity of certain elements of these methods in the elimination of certain pollutants and on the other hand the advantages and limits of these methods. Elements like biochars, biosorbents and composite materials are used due to their very strong porosity which makes it possible for them to develop an important contact surface with the external medium, at low costs, and the possibility of producing them from renewable sources. The latter still run up however against the problems of formation of mud and regeneration. Depollution by magnetic separation is also used due to its capacity to mitigate the disadvantages of certain methods which generally lead to the formation of mud and overcoming also the difficulties like obtaining an active material and at the same time being able to fix the pollutants present in the effluents to treat and sensitize them to external magnetic fields.

Activated carbon enhanced anaerobic digestion of food waste - Laboratory-scale and Pilot-scale operation

Effects of activated carbon (AC) supplementation on anaerobic digestion (AD) of food waste were elucidated in lab- and pilot-scales. Lab-scale AD was performed in 1 L and 8 L digesters, while pilot-scale AD was conducted in a 1000 L digester. Based on the optimal dose of 15 g AC per working volume derived from the 1 L digester, for the same AC dosage in the 8 L digester, an improved operation stability coupled with a higher methane yield was achieved even when digesters without AC supplementation failed after 59 days due to accumulation of substantial organic intermediates. At the same time, color removal from the liquid phase of the digestate was dramatically enhanced and the particle size of the digestate solids was increased by 53% through AC supplementation after running for 59 days. Pyrosequencing of 16S rRNA gene showed the abundance of predominant phyla Firmicutes, Elusimicrobia and Proteobacteria selectively enhanced by 1.7-fold, 2.9-fold and 2.1-fold, respectively. Pilot-scale digester without AC gave an average methane yield of 0.466 L⋅(gVS)^-1⋅d^-1 at a composition of 53-61% v/v methane. With AC augmentation, an increase of 41% in methane yield was achieved in the 1000 L digester under optimal organic loading rate (1.6 g VS_FW·L^-1·d^-1).

Tunable Polarity Carbon Fibers, a Holistic Approach to Environmental Protection

The pollution of environmental resources is an issue of social concern worldwide. Chemistry is essential for the design of decontamination strategies and analytical approaches to detect and monitor the contamination. Sorptive materials are usually required in both approaches and green synthesis should be used to minimize their own environmental impact. Carbon fibers (CFs) obtained by the pyrolysis of natural cellulose-rich materials fulfill these requirements. In this article, thirty CFs obtained under different conditions are chemically characterized and their sorption ability towards selected pollutants, covering a wide range of polarity, is evaluated. This study provides more profound knowledge related to the polarity of these materials, their interactions with chemical substances and allows the prediction of more appropriate materials (pyrolysis temperature and time) in order to remove the given pollutant. Furthermore, the use of CFs as sorptive materials for the extraction of contaminants from water samples to assist with their instrumental detection is outlined. In this sense, the use of CFs and gas chromatography with mass spectrometric detection allows the detection of selected pollutants in the low ng/mL range. Thus, this article provides an integrated approach to the potential of CFs for environmental protection.

Magnetic carboxyl functional nanoporous polymer: synthesis, characterization and its application for methylene blue adsorption

Magnetic carboxyl functional nanoporous polymer (MCFNP) was chemically fabricated by incorporation of magnetic Fe₃O₄ precursor into the carboxyl functional nanoporous polymer (CFNP). The as-synthesized MCFNP was characterized and used as an adsorbent for rapid adsorption removal of methylene blue (MB) from wastewater. Several experimental parameters affecting the adsorption efficiency were investigated including initial pH, adsorbent dosage, initial MB concentration, contact time and temperature. The adsorption behavior of MCFNP displayed that adsorption kinetics and isotherms could be well fitted to the pseudo-second-order and Langmuir models, respectively. The experimental results showed that MCFNP was an effective adsorbent with a maximum adsorption capacity of 57.74 mg g⁻¹ for MB at 298 K. The negative free energy (ΔG) and positive enthalpy change (ΔH) confirmed that the adsorption reaction was a spontaneous and endothermic process. In addition, ethanol was used as an effective extractant for the regeneration of MCFNP, and the adsorption efficiency could remain 80% after the ninth regeneration cycle.

Efficient heavy metal removal from industrial melting effluent using fixed-bed process based on porous hydrogel adsorbents

High adsorption capacity, fast adsorption kinetics, good reusability and low cost are highly demanded for adsorbents used in practical adsorption process. In this study, a porous double network Jute/Polyacrylic acid (Jute/PAA) gel was prepared using simple free-radical polymerization of acrylic acid in Jute aqueous solution. The high permeability of Jute/PAA hydrogel with about 80 wt% water made internal adsorption sites fully expose to metal ions. The Jute/PAA gel adsorbent could efficiently adsorb heavy metals in melting wastewater, especially Cd²⁺ and Pb²⁺. The adsorbent showed very high adsorption capacities of 401.7 mg/g for Cd²⁺ and 542.9 mg/g for Pb²⁺. Moreover, the adsorption equilibrium reached within only 10 min for 40 mg/L of Cd²⁺ and Pb²⁺ using 1 g/L adsorbent. Meanwhile, the removal efficiencies reached 81.0% for Pb (C₀ = 3.825 mg/L), 79.3% for Cd (C₀ = 6.075 mg/L), 83.4% for Cu (C₀ = 9.325 mg/L), 29.8% for Zn (C₀ = 188.6 mg/L), 22.3% for Mn (C₀ = 17.05 mg/L), 96.2% for Cr (C₀ = 0.25 mg/L) and 99.8% for Fe (C₀ = 9.75 mg/L) in melting wastewater using 1 g/L adsorbent in 2 h. In particular, the concentrations of Pb, Cd and Cr decreased below 0.001 mg/L using 4 g/L adsorbent. In the fixed-bed column experiments, the treatment volume of melting wastewater reached 2900 BV (32.8 L) only producing 50 BV (565 mL) eluent. This work develops a highly practical adsorption process based on hydrogel adsorbents for the removal of heavy metals in actual wastewater.

Application of machine/statistical learning, artificial intelligence and statistical experimental design for the modeling and optimization of methylene blue and Cd(ii) removal from a binary aqueous solution by natural walnut carbon

Analytical chemists apply statistical methods for both the validation and prediction of proposed models. Methods are required that are adequate for finding the typical features of a dataset, such as nonlinearities and interactions. Boosted regression trees (BRTs), as an ensemble technique, are fundamentally different to other conventional techniques, with the aim to fit a single parsimonious model. In this work, BRT, artificial neural network (ANN) and response surface methodology (RSM) models have been used for the optimization and/or modeling of the stirring time (min), pH, adsorbent mass (mg) and concentrations of MB and Cd²⁺ ions (mg L^-1) in order to develop respective predictive equations for simulation of the efficiency of MB and Cd²⁺ adsorption based on the experimental data set. Activated carbon, as an adsorbent, was synthesized from walnut wood waste which is abundant, non-toxic, cheap and locally available. This adsorbent was characterized using different techniques such as FT-IR, BET, SEM, point of zero charge (pH_pzc) and also the determination of oxygen containing functional groups. The influence of various parameters (i.e. pH, stirring time, adsorbent mass and concentrations of MB and Cd²⁺ ions) on the percentage removal was calculated by investigation of sensitive function, variable importance rankings (BRT) and analysis of variance (RSM). Furthermore, a central composite design (CCD) combined with a desirability function approach (DFA) as a global optimization technique was used for the simultaneous optimization of the effective parameters. The applicability of the BRT, ANN and RSM models for the description of experimental data was examined using four statistical criteria (absolute average deviation (AAD), mean absolute error (MAE), root mean square error (RMSE) and coefficient of determination (R²)). All three models demonstrated good predictions in this study. The BRT model was more precise compared to the other models and this showed that BRT could be a powerful tool for the modeling and optimizing of removal of MB and Cd(ii). Sensitivity analysis (calculated from the weight of neurons in ANN) confirmed that the adsorbent mass and pH were the essential factors affecting the removal of MB and Cd(ii), with relative importances of 28.82% and 38.34%, respectively. A good agreement (R² > 0.960) between the predicted and experimental values was obtained. Maximum removal (R% > 99) was achieved at an initial dye concentration of 15 mg L^-1, a Cd²⁺ concentration of 20 mg L^-1, a pH of 5.2, an adsorbent mass of 0.55 g and a time of 35 min.

Treatment of dye wastewater using an ultrasonic aided nanoparticle stacked activated carbon: Kinetic and isotherm modelling

The present work explains the biosorption of malachite green dye from aquatic systems by nano zero valent iron stacked activated carbon (NZVI-AC), which was prepared by dual surface modification strategy. NZVI-AC was characterized by using FTIR, SEM-EDX, XRD and TGA. NZVI-AC exhibited efficient performance in dye biosorption properties. Experimental variables such as time, pH, dye concentration, temperature and biosorbent dosage influenced Langmuir adsorption capacity of 187.3 mg/g. The present biosorption system was best described by pseudo-first order kinetics. The dye was completely knocked out of the solution within 60 min at equilibrium. The thermodynamic behaviour of NZVI-AC was exothermic, feasible and spontaneous. Experimental data was engaged to validate new solid-liquid phase equilibrium model, showing the average absolute relative deviation 7.72%. Hence the procedure was non-toxic, potential to retain biosorbent from the solution, applicable for multiple cycles. In context, NZVI-AC can be recommended for the treatment of dyes from industrial effluent.

Pyrolysis/gasification of pine sawdust biomass briquettes under carbon dioxide atmosphere: Study on carbon dioxide reduction (utilization) and biochar briquettes physicochemical properties

In this paper, the effects of temperature and CO₂ content on CO₂ reduction (utilization) efficiency and physicochemical properties of pyrolysis/gasification biochar briquettes were investigated. The CO₂ reduction (utilization) efficiency (CRE) reached the peak value of 74.9% in a 10% CO₂/90% N₂ atmosphere at 600 °C. The crackings of hydroxyl, CC bonds, methyl and methylene groups of biochars briquette were enhanced by high temperature and CO₂. The increase of CO₂ concentration was beneficial for developing biochar microporosity, but not conductive to enhance higher heating value, volume density and durability of biochar briquette. To get a higher CRE and make feasible biochar briquettes are the primary goal for this work. Therefore, the optimal introduced CO₂ to biomass ratio is calculated to be 135 g/kg for experiments done with 10% CO₂ with N₂ at 600 °C.

Amine-functionalized magnetic bamboo-based activated carbon adsorptive removal of ciprofloxacin and norfloxacin: A batch and fixed-bed column study

Amine-functionalized magnetic bamboo-based activated carbon (AFM-BAC) derived from bamboo products wastes were employed for effective adsorption of fluoroquinolone antibiotics ciprofloxacin (CIP) and norfloxacin (NOR) through batch processing. The effects of factors on the adsorption of both antibiotics were studied. The studies of various factors influencing the adsorption behavior indicated that the maximum adsorption capacities for two antibiotics adsorption were observed in weakly acidic condition and the adsorption amounts of two antibiotics increased with the increase of zwitterionic form, implying the importance of zwitterionic form, and the adsorption process is spontaneous and endothermic. The result of date indicated that adsorption of both two antibiotics onto the AFM-BAC better fits Langmuir isotherm model. The saturated magnetization of AFM-BAC reached 8.55 emu g^-1. A fixed-bed column adsorption with a bench-scale was carried out. Desorption and regeneration experiments showed that the AFM-BAC for both antibiotics could remain above 80% after five consecutive recycling cycles.

A novel biodegradable arsenic adsorbent by immobilization of iron oxyhydroxide (FeOOH) on the root powder of long-root Eichhornia crassipes

In this study, FeOOH was immobilized on the biodegradable root powder, abbreviated as RP, of long-root Eichhornia crassipes, a kind of waste biomass, to improve the adsorption performances for aqueous arsenic contaminants. The adsorption kinetics and thermodynamics experiments showed that the adsorption rates and capacities of the root powder for arsenate (As(V)) and arsenite (As(III)) were both enhanced markedly after modification with FeOOH. The adsorption of As(V) and As(III) by the modified root powder, abbreviated as MRP, could arrive at equilibrium in 50 min and the saturated adsorption capacities reached up to 8.67-9.43 mg/g for As(V) and 5.21-5.65 mg/g for As(V) at temperature of 10-50 °C, respectively. Besides, the effect of pH and ionic strength on adsorption was investigated and the results showed that the optimum pH for the arsenic adsorption using the MRP was 9.0 and the As(V) adsorption was more sensitive to ionic strength. Furthermore, the complexation of hydratable hydroxyls on FeOOH with arsenic contaminants was concluded as the adsorption force according FTIR and XPS analyses. The MRP used could be regenerated via 0.4 mol/L NaOH solution and no apparent adsorption capacity losses appeared after 6 cyclic utilizations.

One-pot synthesis of a highly porous anionic hypercrosslinked polymer for ultrafast adsorption of organic pollutants

Ultrafast adsorption of organic pollutants in water was achieved with a highly porous anionic hypercrosslinked polymer as an adsorbent.

Relationship of cellulose and lignin contents in biomass to the structure and RB-19 adsorption behavior of activated carbon

Activated carbon microspheres prepared from biomass resources serve as green, highly efficient, and reusable adsorbents for reactive blue 19.

Fast removal of methylene blue from aqueous solution using coal-based activated carbon

Coal-based activated carbons (CACs) were prepared from three long flame coals with different ash and volatile matter content. CACs prepared by coal with high ash (6.74%) and volatile matter content (34.31%) showed better adsorption efficiency towards MB (547.35 mg g⁻¹) due to higher surface area and pore volume. The effect of coal to activating agent ratio (CAR) was also investigated in a batch reactor. The porosity development is closely related to the CAR. The calculated monolayer adsorption amount (714.29 mg g⁻¹) was found on YLC-AC-3 with a surface area of 1212.50 m² g⁻¹. The equilibrium data were favorably described by the Langmuir and Freundlich isotherm models, and adsorption kinetics fitted well to the pseudo-second order model. The removal efficiency remains at 98.21% after five runs. The results of the present study suggest that CACs are potential and effective adsorbents in fast removal of dyes from aqueous solution.

A monolayer adsorption amount of MB (714.29 mg g⁻¹) was found on a coal-based activated carbon prepared by a simple method.

Broadening the pore size of coal-based activated carbonviaa washing-free chem-physical activation method for high-capacity dye adsorption

Aiming to overcome the limitations of the narrow pore size distributions of traditional activated carbon materials and to achieve wide adaptabilities towards large molecules adsorption, we herein demonstrate a new type of activated carbon with a broadened pore size distribution for high-rate and high-capacity aqueous dye molecule (Rhodamine B) adsorption. The preparation of CP-AC is achieved by a facile and one-step mineral-assisted chem-physical activation strategy from Chinese large-reserve Zhundong coal with ZnCl₂ and CO₂ as the activation agents. The method yields the activated carbon (CP-AC) that has a pore-size broadened hierarchical pore configuration with a high surface area and a large pore volume, favorably enabling a high-capacity Rhodamine B adsorption up to 881 mg g⁻¹, which is among the highest levels of the reported activated carbons. A sonication-assisted adsorption test further demonstrates the high-rate adsorption capability of CP-AC with Rhodamine B adsorption capacity up to 842 mg g⁻¹ within 30 min (96% of the saturation capacity) while microporous activated carbon obtained by solely ZnCl₂ activation could just achieve a capacity of 374 mg g⁻¹ within 30 min. In virtue of the low-cost resource materials and washing-free craft, this work offers a simple and green preparation strategy towards high-performance coal based activated carbons, holding great potentials for the industrial production and applications.

Aiming to overcome the limitations of the narrow pore size distributions of traditional activated carbon, we demonstrate a new type of activated carbon with a broadened pore size distribution for high-rate and high-capacity aqueous dye adsorption.

Utilization of modified Dioscorea opposita Thunb. as a novel biosorbent for the adsorption of indigo carmine in aqueous solutions

It is important to identify efficient adsorbents for the removal of dyestuffs from aqueous solutions as this kind of pollution becomes more extensive. In this study, Dioscorea opposita Thunb. (DOT) was modified with polyethylene imine (DOT@PEI) as a novel biosorbent to remove the typical anionic dye indigo carmine (IC) from wastewater. The modified DOT@PEI biosorbent was characterized using BET (Brunauer–Emmett–Teller), SEM (scanning electron microscopy), EDS (energy dispersive spectroscopy), and FTIR (Fourier transform infrared spectroscopy) methods, and the results demonstrated that DOT@PEI is an excellent biosorbent. Batch adsorption studies showed that optimum adsorption parameters were pH 2.0, 1.0 g L⁻¹ dosage, and temperature of 20 °C. The isothermal adsorption data showed good fitting to the Langmuir model, with a maximum adsorption capability of 344.83 mg g⁻¹ for IC. Kinetic experiments showed that the experimental data fitted well to a pseudo-second-order kinetic model and the thermodynamic parameters indicated that adsorption is a spontaneous exothermic process. Adsorption–desorption experiments illustrated the good regeneration capability of DOT@PEI. These results demonstrate that DOT@PEI can be used as an effective biosorbent in water for the removal of anionic dyes such as required for environmental applications.

It is important to identify efficient adsorbents for the removal of dyestuffs from aqueous solutions as this kind of pollution becomes more extensive.

A critical review on sustainable biochar system through gasification: Energy and environmental applications

This review lays great emphasis on production and characteristics of biochar through gasification. Specifically, the physicochemical properties and yield of biochar through the diverse gasification conditions associated with various types of biomass were extensively evaluated. In addition, potential application scenarios of biochar through gasification were explored and their environmental implications were discussed. To qualitatively evaluate biochar sustainability through the gasification process, all gasification products (i.e., syngas and biochar) were evaluated via life cycle assessment (LCA). A concept of balancing syngas and biochar production for an economically and environmentally feasible gasification system was proposed and relevant challenges and solutions were suggested in this review.

A versatile bio-based material for efficiently removing toxic dyes, heavy metal ions and emulsified oil droplets from water simultaneously

Developing versatile materials for effective water purification is significant for environment and water source protection. Herein, a versatile bio-based material (CH-PAA-T) was reported by simple thermal cross-linking chitosan and polyacrylic acid which exhibits excellent performances for removing insoluble oil, soluble toxic dyes and heavy metal ions from water, simultaneously. The adsorption capacities are 990.1mgg^-1 for methylene blue (MB) and 135.9mgg^-1 for Cu²⁺, which are higher than most of present advanced absorbents. The adsorption towards organic dyes possesses high selectivity which makes CH-PAA-T be able to efficiently separate dye mixtures. The stable superoleophobicity under water endows CH-PAA-T good performance to separate toluene-in-water emulsion stabilized by Tween 80. Moreover, CH-PAA-T can be recycled for 10 times with negligible reduction of efficiency. Such versatile bio-based material is a potential candidate for water purification.

Synthesis and characterization of slow pyrolysis pine cone bio-char in the removal of organic and inorganic pollutants from aqueous solution by adsorption: Kinetic, equilibrium, mechanism and thermodynamic

Pine cone bio-char was synthesized through slow pyrolysis at 500°C, characterized and used as an effective adsorbent in the removal of organic Methylene Blue (MB) dye and inorganic nickel metal (Ni(II) ions from aqueous phase. Batch adsorption kinetic study was carried out by varying solution pH, dye concentration, temperature, adsorbent dose and contact time. Kinetic and isotherm models indicates that the adsorption of both adsorbates onto pine cone bio-char were mainly by chemisorption. Langmuir maximum adsorption capability was found to be 106.4 and 117.7mg/g for Methylene Blue (MB) and nickel ions (NI(II) respectively. Thermodynamic parameters suggested that the adsorption was an endothermic and spontaneous. These results indicate the applicability of pine cone as a cheap precursor for the sustainable production of cost-effective and environmental friendly bio-char adsorbent.

Human hair-derived high surface area porous carbon material for the adsorption isotherm and kinetics of tetracycline antibiotics

In this work, a human hair-derived high surface area porous carbon material (HHC) was prepared using potassium hydroxide activation. The morphology and textural properties of the HHC structure, along with its adsorption performance for tetracycline (TC) antibiotics, were evaluated. HHC showed a high surface area of 1505.11m²/g and 68.34% microporosity. The effects of most important variables, such as initial concentration (25-355mg/L), solution pH (3-13), and temperatures (30-50°C), on the HHC adsorption performance were investigated. Isotherm data analysis revealed the favorable application of the Langmuir model, with maximum TC uptakes of 128.52, 162.62, and 210.18mg/g at 30, 40, and 50°C, respectively. The experimental data of TC uptakes versus time were analyzed efficiently using a pseudo-first order model. Porous HHC could be an efficient adsorbent for eliminating antibiotic pollutants in wastewater.

An environmental friendly animal waste disposal process with ammonia recovery and energy production: Experimental study and economic analysis

Animal manure waste is considered as an environmental challenge especially in farming areas mainly because of gaseous emission and water pollution. Among all the pollutants emitted from manure waste, ammonia is of greatest concern as it could contribute to formation of aerosols in the air and could hardly be controlled by traditional disposal methods like landfill or composting. On the other hand, manure waste is also a renewable source for energy production. In this work, an environmental friendly animal waste disposal process with combined ammonia recovery and energy production was proposed and investigated both experimentally and economically. Lab-scale feasibility study results showed that 70% of ammonia in the manure waste could be converted to struvite as fertilizer, while solid manure waste was successfully gasified in a 10kW downdraft fixed-bed gasifier producing syngas with the higher heating value of 4.9MJ/(Nm³). Based on experimental results, economic study for the system was carried out using a cost-benefit analysis to investigate the financial feasibility based on a Singapore case study. In addition, for comparison, schemes of gasification without ammonia removal and incineration were also studied for manure waste disposal. The results showed that the proposed gasification-based manure waste treatment process integrated with ammonia recovery was most financially viable.

Carboxylic acid functionalized sesame straw: A sustainable cost-effective bioadsorbent with superior dye adsorption capacity

This study prepared a carboxylic functionalized bioadsorbent that met the "4-E" criteria: Efficient, Economical, Environmentally friendly, and Easily-produced. Sesame straw (Sesamum indicum L.) was functionalized through treatment with citric acid (SSCA) and tartaric acid (SSTA). The products were examined for adsorption capacity and mechanisms. Langmuir model gave the best fit for the isotherm data, and the maximum monolayer adsorption capacity of SSCA was 650mgg^-1 for methylene blue (MB). The excellent dye adsorption capacity of SSCA can be attributed to the introduction of ester groups during citric-acid modification and the tube-like structures (i.e., sesame straw cell wall remnants). At last, the cost of carboxylic acid functionalized bioadsorbents was evaluated, which showed that SSCA would be the most cost-effective bioadsorbent. Additionally, this study presents a thermo-decomposition methodology for contaminant-loaded bioadsorbent. Results showed that SSCA is probably one of the few bioadsorbents that can be produced and applied in industrial scale.

Cellulose nanocrystal-reinforced keratin bioadsorbent for effective removal of dyes from aqueous solution

High-efficiency and recyclable three-dimensional bioadsorbents were prepared by incorporating cellulose nanocrystal (CNC) as reinforcements in keratin sponge matrix to remove dyes from aqueous solution. Adsorption performance of dyes by CNC-reinforced keratin bioadsorbent was improved significantly as a result of adding CNC as filler. Batch adsorption results showed that the adsorption capacities for Reactive Black 5 and Direct Red 80 by the bioadsorbent were 1201 and 1070mgg^-1, respectively. The isotherms and kinetics for adsorption of both dyes on bioadsorbent followed the Langmuir isotherm model and pseudo-second order model, respectively. Desorption and regeneration experiments showed that the removal efficiencies of the bioadsorbent for both dyes could remain above 80% at the fifth recycling cycles. Moreover, the bioadsorbent possessed excellent packed-bed column operation performance. Those results suggested that the adsorbent could be considered as a high-performance and promising candidate for dye wastewater treatment.